[StBernard] 100 yr storm model

[Westley Annis]

Westley,

some time ago there was some discussion about what the percentages of experiencing a 100 yr storm were over time.  There was some belief that each year the chance to experience the 100 yr storm goes up if the previous yr(s) did not produce such a storm.  This is not how the modeling works and I have forwarded a caption from the engineering description of the modeling.

The 100-yr design elevations are those elevations required to provide protection from a hurricane event that would produce a 1% exceedence surge elevation and associated waves.  The design elevations include components of surge, wave and wind setup, wave run-up, a component for runoff if required, uncertainty and future conditions.  The 1% exceedence elevation (100-yr storm) translates to a storm event having a 1% chance of occurring in any given year and is independent of previous or future years.  As such, the chance of the 1% exceedence does not increase over time.

For what is worth.

God Bless,
Craig